Wireless communication device

ABSTRACT

The invention includes a first circuit board on which a plurality of first terminal sections is arranged, a high-frequency circuit arranged on the first circuit board and connected to at least one of the plurality of first terminal sections, a second circuit board on which is arranged a plurality of second terminal sections facing the plurality of first terminal sections, a first internal circuit arranged on the second circuit board and connected to at least one of the plurality of second terminal sections, and electrical continuity unit providing electrical continuity among the plurality of first terminal sections and the plurality of second terminal sections. At least two contiguous terminals of the plurality of first terminal sections and/or the plurality of second terminal sections including a terminal connected to the high-frequency circuit are connected via a capacitor and function as an antenna for wireless communication.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2010-255596 filed on Nov. 16, 2010. The entire disclosure of JapanesePatent Application No. 2010-255596 is hereby incorporated herein byreference.

BACKGROUND

1. Technological Field

The present invention relates to a wireless communication device.

2. Background Technology

Wireless communication devices have become progressively smaller in sizein recent years, to the point where wristwatch-type devices are nowavailable. While high-density mounting is essential for the purpose ofsize and weight reduction, antenna construction is crucial for improvingreceiving sensitivity in extreme reception environments. For example, aconstruction for arranging an antenna of a compact wirelesscommunication device has been shown (see, for example, Patent Citation1).

Japanese Patent Application Publication No. 2007-274609 (PatentCitation 1) is an example of the related art.

SUMMARY Problems to be Solved by the Invention

However, the construction of Patent Citation 1 requires an antennaelement such as a chip antenna or the like, and moreover requires meansfor connecting the antenna and a high-frequency circuit, posing a riskof difficulty in reducing size, weight, and cost.

Means Used to Solve the Above-Mentioned Problems

The present invention is directed to addressing the aforementionedproblem at least in part, with realization possible according to thefollowing modes.

First Mode

A wireless communication device including: a first circuit board onwhich a plurality of first terminal sections is arranged; ahigh-frequency circuit arranged on the first circuit board and connectedto at least one of the plurality of first terminal sections; a secondcircuit board on which is arranged a plurality of second terminalsections facing the plurality of first terminal sections; a firstinternal circuit arranged on the second circuit board and connected toat least one of the plurality of second terminal sections; andelectrical continuity unit providing electrical continuity among theplurality of first terminal sections and the plurality of secondterminal sections; wherein at least two contiguous terminals from amongthe plurality of first terminal sections and/or the plurality of secondterminal sections including a terminal that is connected to thehigh-frequency circuit are connected via a capacitor; and the twocontiguous terminals connected via the capacitor function as an antennafor wireless communication.

According to this mode, in a compact wireless communication device, atleast two contiguous terminals from among the plurality of firstterminal sections and/or the plurality of second terminal sectionsconnected with electrical continuity unit is used for an antenna,obviating the need for an antenna element such as a chip antenna, andobviating the need for antenna connection unit, and making possible aninstrument having smaller size and weight, and lower cost.

Second Mode

The aforedescribed wireless communication device, wherein at least partof the electrical continuity unit functions as an antenna for wirelesscommunication.

According to this mode, the electrical continuity unit is typicallyarranged in an outside peripheral section of the first circuit board.This position is close to free space and away from ICs such as the CPU,which is a source of noise. Consequently, where used to function as anantenna, antenna performance can be improved further.

Third Mode

The aforedescribed wireless communication device, wherein the pluralityof first terminal sections is arranged in outside peripheral sections ofthe first circuit board.

According to this mode, by selecting a high-performance antennaconfiguration, transmission efficiency and receiving sensitivity of thehigh-frequency circuit can be improved.

Fourth Mode

The aforedescribed wireless communication device, wherein the antenna isa dipole antenna.

According to this mode, the high-performance antenna element affordsimproved transmission efficiency and receiving sensitivity of thehigh-frequency circuit. With a monopole antenna, GND of large surfacearea is necessary to attain such performance, and this is difficult toadequately ensure in a compact wireless communication device such as oneof wristwatch type. A dipole antenna, on the other hand, substantiallyrequires no GND, and is therefore suited for a compact wirelesscommunication device such as one of wristwatch type.

Fifth Mode

The aforedescribed wireless communication device, wherein the antenna isa diversity antenna.

According to this mode, an antenna element with good reception statuscan be selected to thereby serve as a high-performance antenna elementaffording improved transmission efficiency and receiving sensitivity ofthe high-frequency circuit.

Sixth Mode

The aforedescribed wireless communication device, wherein the wirelesscommunication device includes a second internal circuit arranged on thefirst circuit board, connected to at least one of the plurality of firstterminal sections, and adapted to output a direct current signal or alow-frequency signal; and further includes first high-frequency cutoffelements connected at a first end to the second terminal sections and atanother end to the first internal circuit; and/or second high-frequencycutoff elements connected at a first end to the first terminal sectionsand at another end to the second internal circuit.

According to this mode, the high-frequency circuit and the antennafunction are connected via the second terminal sections on the face ofthe second circuit board which is connected to the first internalcircuit via the first high-frequency cutoff element, thereby providingfrequency separation between the direct current signal or low-frequencysignal of the signal input to the first internal circuit, and thehigh-frequency signal used in the high-frequency circuit. Also, becausethe high-frequency circuit and the antenna function are connected viathe first terminal sections on the face of the first circuit board whichis connected to the second internal circuit via the secondhigh-frequency cutoff element, frequency separation is provided betweenthe direct current signal or low-frequency signal of the signal input tothe second internal circuit, and the high-frequency signal used in thehigh-frequency circuit.

Seventh Mode

The aforedescribed wireless communication device, wherein the first andsecond high-frequency cutoff elements are inductance elements.

According to this mode, the inductance elements have the action oflow-pass filters. Specifically, the elements provide high impedance inrelation to frequency components of a high-frequency signal, and lowimpedance in relation to frequency components of a direct current signalor low-frequency signal; therefore, it is possible to prevent thehigh-frequency signal leakage to the first and second internal circuits,and it is possible to pass the direct current signal or low-frequencysignal applied to the first and second terminal sections to the firstand second internal circuits.

Eighth Mode

The aforedescribed wireless communication device, wherein the first andsecond high-frequency cutoff elements are resistance elements.

According to this mode, the resistance elements have the function ofcutting off high-frequency signals (large current magnitude). Also,because the current flowing to the first and second internal circuits isvery small, moderate resistance values can be permitted, and thereforethe direct current signal or low-frequency signal applied to the firstand second terminal sections can be caused to flow to the first andsecond internal circuits.

Ninth Mode

The aforedescribed wireless communication device, wherein the firstinternal circuit is a display section, and the second internal circuitis a digital IC for signal processing.

According to this mode, information inside the wireless communicationdevice can be visually confirmed and digitally signal-processed.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a descriptive diagram showing an overall configuration of awrist-worn wireless communication device according to a firstembodiment;

FIG. 2 is a front view and a bottom view showing a circuit assembly onboard the wrist-worn wireless communication device according to thefirst embodiment;

FIG. 3 is a top view of the wrist-worn wireless communication deviceaccording to the first embodiment;

FIG. 4 is a top view of the wrist-worn wireless communication deviceaccording to the first embodiment;

FIG. 5 is a top view of the wrist-worn wireless communication deviceaccording to the first embodiment;

FIG. 6 is a top view and cross sectional view of a wrist-worn wirelesscommunication device according to a second embodiment;

FIG. 7 is a cross sectional view of a wrist-worn wireless communicationdevice according to a third embodiment;

FIG. 8 is a top view of the wrist-worn wireless communication deviceaccording to the third embodiment;

FIG. 9 is a top view of a wrist-worn wireless communication deviceaccording to a fourth embodiment;

FIG. 10 is a cross sectional view of a wrist-worn wireless communicationdevice according to a fifth embodiment;

FIG. 11 is a top view of a wrist-worn wireless communication deviceaccording to a sixth embodiment;

FIG. 12 is a diagram showing a configuration of an antenna according toa seventh embodiment; and

FIG. 13 is a diagram showing a configuration of an antenna according toan eighth embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Based on the drawings, a wrist-worn wireless communication device isdescribed below by way of a wireless communication device according tothe present embodiment.

First Embodiment

FIG. 1 is a descriptive diagram showing an overall configuration of awrist-worn wireless communication device according to the presentembodiment. FIG. 2 is a front view and a bottom view showing a circuitassembly on board the wrist-worn wireless communication device accordingto the present embodiment.

The wrist-worn wireless communication device 2 according to the presentembodiment comprises a device main body 12, the side at which a liquidcrystal panel (display section) (first internal circuit) 10 is disposedbeing considered the front side; and a pair of wrist bands 14R, 14L. Therespective wrist bands 14R, 14L are attached at the basal end of eachband to either end of the device main body 12, and it is possible forthe bands to be joined to one another at their distal end sections by abuckle 16.

The device main body 12 comprises a front side casing 18, and a backcover 20 affixed to the back side of the casing 18 at the back side ofthe device main body 12. The device main body 12, which comprises thecasing 18 and the back cover 20, houses a circuit assembly 22. Thecircuit assembly 22 has a construction in which the principalconstituent components thereof are disposed in a stack in the thicknessdirection thereof inside the device main body 12. Specifically, as shownin FIG. 2, the circuit assembly 22 includes the liquid crystal panel 10,a circuit board (first circuit board 24), and a circuit driving cell 26disposed in the thickness direction.

FIG. 3 is a top view of the wrist-worn wireless communication device 2according to the present embodiment. The wrist-worn wirelesscommunication device 2 is provided with the circuit board 24 and with adisplay panel board (second circuit board) 32. On the circuit board 24are disposed various integrated circuits (ICs; discussed later), andcircuit-board-side terminals. A multilayer board is used as the circuitboard 24, with a surface layer pattern (wiring pattern) formed on aboard composed of a glass-epoxy board, a phenolic resin board, or aceramic board.

On the display panel board 32 are disposed the liquid crystal panel 10,and display panel-side terminals, discussed later.

Typically, the circuit-board-side terminals on the circuit board 24 andthe display panel-side terminals on the display panel board 32 areconnected by “a rubber connector of alternating stacked layers ofconductive silicone rubber using metal particles as the conductor, andelectrically insulating silicone rubber, in a zebra arrangement”(commonly known as a zebra, and herein referred to as a zebra connector(electrical continuity unit). Here, because the signals supplied to theliquid crystal panel 10 are either direct current signals orlow-frequency signals (1 MHz or below), frequency separation from thehigh-frequency signals currently used in ordinary wirelesscommunications, for example, 2.4 GHz can be provided.

FIG. 4 is a top view of the wrist-worn wireless communication device 2according to the present embodiment. FIG. 4 depicts a state with thedisplay panel board 32 detached from the circuit board 24. On thecircuit board 24 are disposed a high-frequency analog IC 36 providedwith transmitting and receiving functions; circuit-board-side terminals28; and wiring 52 connecting the high-frequency analog IC 36 to acircuit-board-side terminal 28. The high-frequency analog IC 36transmits and receives high-frequency signals (RF signals) of 2.4 GHz,for example.

The circuit-board-side terminals 28 function as connecting terminals forthe circuit board 24 and the display panel board 32, and also functionas the antenna of the wrist-worn wireless communication device 2. Asshall be apparent, the plurality of circuit-board-side terminals 28 isseparated in order to transmit respectively different signals.Consequently, in unmodified form they cannot function as an antenna.Accordingly, the plurality of circuit-board-side terminals 28 isconnected by small-capacity coupling capacitors 68. Specifically, theyare connected in a high-frequency manner. Meanwhile, because the signalsapplied to the circuit-board-side terminals 28 are direct currentsignals or low-voltage signals, there is no risk of problems arising inrelation to function, despite the terminals being coupled by thesmall-capacity coupling capacitors 68. Moreover, antenna length; i.e.,frequency, can be adjusted through the number of coupling capacitors 68which connect the plurality of circuit-board-side terminals 28.

Typically, the circuit-board-side terminals 28 are arranged in outsideperipheral sections of the circuit board 24. These positions are closeto free space and away from ICs such as a CPU, which is a source ofnoise. Consequently, where such a configuration is used for an antenna,antenna performance can be improved.

FIG. 5 is a top view of the wrist-worn wireless communication device 2according to the present embodiment. FIG. 5 depicts a state with thedisplay panel board 32 detached from the circuit board 24. On thecircuit board 24 is disposed a signal processing digital IC (secondinternal circuit) 38. The signal processing digital IC 38 incorporatesdigital circuitry for sampling a reception signal prior toanalog/digital conversion, as well as phased-lock loop circuitry and thelike.

In order to reliably prevent high-frequency signal leakage to the signalprocessing digital IC 38, in cases where, viewed from the high-frequencyanalog IC 36, impedance of the signal processing digital IC 38 on thecircuit board 24 is low or lines are long, inductance elements 46 orresistance elements 48 may be interposed as second high-frequency cutoffelements between the signal processing digital IC 38 and thecircuit-board-side terminals 28. The signals supplied to the signalprocessing digital IC 38 are direct current signals or low-frequencysignals, and moreover the electrical current is very low, andaccordingly there is substantially no risk of problems arising frominterposition of the inductance elements 46 or resistance elements 48.

In the present embodiment, as there is a risk of high-frequency signalleakage to the display panel board 32 via the zebra connector, it ispreferable for the zebra connector to have high resistance or be giveninductance characteristics. In this case as well, the signals suppliedto the liquid crystal panel 10 are direct current signals orlow-frequency signals, and moreover the electrical current is very low,and accordingly there is substantially no risk of problems arising.

In the wrist-worn wireless communication device 2 according to thepresent embodiment, at least one space between contiguous terminals fromamong the plurality of circuit-board-side terminals 28 is used for anantenna, thereby obviating the need for an antenna element such as achip antenna, as well as obviating the need for antenna connection unit,and making possible an instrument having smaller size and weight, andlower cost.

Second Embodiment

FIG. 6 is a top view and cross sectional view of a wrist-worn wirelesscommunication device according to the present embodiment. FIG. 6A is atop view, FIG. 6B is a cross sectional view, and FIG. 6C is a diagramshowing capacitive coupling. FIG. 6 depicts a state with the displaypanel board 32 detached from the circuit board 24. In the description ofthe present embodiment, configurations like those in thepreviously-described embodiment are assigned like symbols, and are notdescribed.

As shown in FIG. 6A, in place of the coupling capacitors 68 of thepreviously-described wrist-worn wireless communication device 2, thewrist-worn wireless communication device 4 according to the presentembodiment is furnished with a pattern (conductor) 64 on an outer layer(or an inner layer) of the circuit board 24 in a section thereof facingthe circuit-board-side terminals 28. In so doing, by providingcapacitive coupling among the circuit-board-side terminals 28 asdepicted in FIG. 6C, the circuit-board-side terminals 28 can be made tofunction as an antenna.

Here, capacitive coupling will be described. The capacity of a planarcapacitor is C=ε×ε₀×S/d. Here, ε is relative permittivity, ε₀ ispermittivity of vacuum, S is surface area of the circuit-board-sideterminals 28, and d is distance between the pattern 64 and thecircuit-board-side terminals 28. Where a high-permittivity board is usedas the circuit board 24, and ε is 30, S is 0.4 mm² (length 2 mm, width0.2 mm), and d is 0.01 mm, capacity will be approximately 10.6 pF. Inthis case, the impedance of 2.4 GHz is Z=1/jωC. Here, ω is angularfrequency, and with approximately 6 ohms per capacitor, thecircuit-board-side terminals 28 can be connected with sufficiently lowimpedance of approximately 12 ohms between them. The plurality ofcircuit-board-side terminals 28 is connected in a high-frequency mannerby this capacity.

Meanwhile, because the signals applied to the circuit-board-sideterminals 28 are direct current signals or low-frequency signals, thereis no risk of problems arising from coupling by capacity of this orderof magnitude. For example, where frequency is 1 MHz, impedance percapacitor is approximately 15 Mohm to give approximately 30 Mohm betweenthe circuit-board-side terminals 28, which may be viewed as asubstantially open circuit.

The antenna length, that is, the frequency, can be adjusted through thelength of the pattern 64. For example, the wavelength in vacuum λ of 2.4GHz is 12.5 cm. The required length of a monopole antenna is λ/4, and istherefore 3.125 cm. Here, where a glass-epoxy board is used for example,assuming relative permittivity εr of 4.7, antenna required length is3.125/4.7^(1/2) or 1.44 cm. Or, where a ceramic board is used forexample, assuming relative permittivity εr of 30, antenna requiredlength is 3.125/30^(1/2) or 0.57 cm.

According to the present embodiment, there is no need for mounting ofcapacitors, and it is therefore possible to further reduce size, weight,and cost of the device.

Third Embodiment

FIG. 7 is a cross sectional view of a wrist-worn wireless communicationdevice according to the present embodiment. In the description of thepresent embodiment, configurations like those in thepreviously-described embodiments are assigned like symbols, and are notdescribed.

The wrist-worn wireless communication device 4 according to the presentembodiment has disposed therein a zebra connector 42 for connecting thecircuit-board-side terminals 28 on the circuit board 24 with the displaypanel-side terminals 40 on the display panel board 32. In the wrist-wornwireless communication device 4, in addition to the arrangements taughtin the second embodiment, the zebra connector 42 is itself used tofunction as an antenna. Typically, the zebra connector 42 is arranged inan outside peripheral section of the circuit board 24. This position isclose to free space and away from ICs such as a CPU, which is a sourceof noise. Consequently, antenna performance can be further improved incases where the zebra connector 42 is used in manner such as to functionas an antenna. Moreover, antenna performance improves owing to increasedcubic volume of the conductor used to function as an antenna, due to thezebra connector 42. In this case, it is preferable for the zebraconnector 42 to have low resistance.

FIG. 8 is a top view of the wrist-worn wireless communication device 4according to the present embodiment. In order to reliably preventhigh-frequency signal leakage to the liquid crystal display panel 10, incases where, viewed from the high-frequency analog IC 36 (see FIG. 6A),impedance of the liquid crystal display panel 10 on the display panelboard 32 is low or lines are long, inductance elements 46 or resistanceelements 48 may be interposed as first high-frequency cutoff elementsbetween the liquid crystal display panel 10 and the display panel-sideterminals 40. The signals supplied to the liquid crystal display panel10 are direct current signals or low-frequency signals, and moreover theelectrical current is very low, and accordingly there is substantiallyno risk of problems arising from interposition of the inductanceelements 46 or resistance elements 48.

Fourth Embodiment

FIG. 9 is a top view of a wrist-worn wireless communication deviceaccording to the present embodiment. In the description of the presentembodiment, configurations like those in the previously-describedembodiments are assigned like symbols, and are not described.

In addition to the arrangements of the wrist-worn wireless communicationdevice 4 discussed previously, the wrist-worn wireless communicationdevice 6 according to the present embodiment has coupling capacitors 68mounted between the display panel-side terminals 40 of the display panelboard 32. In so doing, the wrist-worn wireless communication device 6has double the capacity of the coupling capacitors than in thewrist-worn wireless communication device 4 discussed previously.Consequently, when this configuration is used to function as an antenna,antenna performance can be further improved.

Fifth Embodiment

FIG. 10 is a cross sectional view of a wrist-worn wireless communicationdevice according to the present embodiment. FIG. 10B is a diagramshowing capacitive coupling. In the description of the presentembodiment, configurations like those in the previously-describedembodiments are assigned like symbols, and are not described.

As shown in FIG. 10A, in place of the coupling capacitors 68 of thewrist-worn wireless communication device 6 discussed previously, thewrist-worn wireless communication device 8 according to the presentembodiment is furnished with a pattern (conductor) 64 on an outer layer(or an inner layer) of the display panel board 32 in a section thereoffacing the display panel-side terminals 40. In so doing, by providingcapacitive coupling among the display panel-side terminals 40 asdepicted in FIG. 10B, the display panel-side terminals 40 can be made tofunction as an antenna.

According to the present embodiment, there is no need for mounting ofcapacitors, and it is therefore possible to further reduce size, weight,and cost of the device.

Sixth Embodiment

FIG. 11 is a top view of a wrist-worn wireless communication deviceaccording to the present embodiment. In the description of the presentembodiment, configurations like those in the previously-describedembodiments are assigned like symbols, and are not described.

Typically, connections between the circuit board 24 and the displaypanel board 32 are carried out in pairs at top and bottom or at left andright. In the wrist-worn wireless communication device 9 according tothe present embodiment, the respective circuit-board-side terminals 28are used to function as an antenna. As shall be apparent, implementationin the first to fifth embodiments is possible as well.

Seventh Embodiment

FIG. 12 is a diagram showing a configuration of an antenna according tothe present embodiment. In the description of the present embodiment,configurations like those in the previously-described embodiments areassigned like symbols, and are not described.

As shown in FIG. 12, the wrist-worn wireless communication device 9according to the present embodiment is configured such thatcircuit-board-side terminals 28 at two locations function as a dipoleantenna 54. In so doing, there is afforded a high-performance antennawhereby transmission efficiency and receiving sensitivity are improved.With a monopole antenna, GND of large surface area is necessary toattain such performance, and this is difficult to adequately ensure in acompact wireless communication device such as a wrist-worn wirelesscommunication device. A dipole antenna, on the other hand, substantiallyrequires no GND, and is therefore suited for a compact wirelesscommunication device such as a wrist-worn wireless communication device.

Eighth Embodiment

FIG. 13 is a diagram showing a configuration of an antenna according tothe present embodiment. In the description of the present embodiment,configurations like those in the previously-described embodiments areassigned like symbols, and are not described.

As shown in FIG. 13, the wrist-worn wireless communication device 9according to the present embodiment is configured such thatcircuit-board-side terminals 28 at two locations function as a diversityantenna 56. In so doing, signals may be input by two radio receptionroutes, and therefore the antenna function having better receptionstatus can be selected, therefore affording a high-performance antennawhereby transmission efficiency and receiving sensitivity are improved.

Apart from the wrist-worn wireless communication device as shown above,other wireless communication devices that can utilize the presentembodiment include pagers (mobile compact wireless paging devices),telephones, televisions, Global Positioning System (GPS) or othersatellite receivers, wireless LANs, and other devices usinghigh-frequency circuits and antenna elements in a limited space.

1. A wireless communication device including: a first circuit board onwhich a plurality of first terminal sections is arranged; ahigh-frequency circuit arranged on the first circuit board and connectedto at least one of the plurality of first terminal sections; a secondcircuit board on which is arranged a plurality of second terminalsections facing the plurality of first terminal sections; a firstinternal circuit arranged on the second circuit board and connected toat least one of the plurality of second terminal sections; andelectrical continuity unit providing electrical continuity among theplurality of first terminal sections and the plurality of secondterminal sections; wherein at least two contiguous terminals from amongthe plurality of first terminal sections and/or the plurality of secondterminal sections including a terminal that is connected to thehigh-frequency circuit are connected via a capacitor; and the twocontiguous terminals connected via the capacitor function as an antennafor wireless communication.
 2. The wireless communication deviceaccording to claim 1, wherein at least part of the electrical continuityunit functions as an antenna for wireless communication.
 3. The wirelesscommunication device according to claim 1, wherein the plurality offirst terminal sections is arranged in outside peripheral sections ofthe first circuit board.
 4. The wireless communication device accordingto claim 3, wherein the antenna is a dipole antenna.
 5. The wirelesscommunication device according to claim 3, wherein the antenna is adiversity antenna.
 6. The wireless communication device according toclaim 1, wherein the wireless communication device includes a secondinternal circuit arranged on the first circuit board, connected to atleast one of the plurality of first terminal sections, and adapted tooutput a direct current signal or a low-frequency signal; and furtherincludes first high-frequency cutoff elements connected at a first endto the second terminal sections and at another end to the first internalcircuit; and/or second high-frequency cutoff elements connected at afirst end to the first terminal sections and at another end to thesecond internal circuit.
 7. The wireless communication device accordingto claim 6, wherein the first and second high-frequency cutoff elementsare inductance elements.
 8. The wireless communication device accordingto claim 6, wherein the first and second high-frequency cutoff elementsare resistance elements.
 9. The wireless communication device accordingto claim 1, wherein the first internal circuit is a display section; andthe second internal circuit is a digital IC for signal processing.